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[操作系统]android 进程间通信数据(一)


关于parcel,我们先来讲讲它的“父辈” Serialize。

Serialize 是java提供的一套序列化机制。但是为什么要序列化,怎么序列化,序列化是怎么做到的,我们将在本文探讨下。

一:java 中的serialize

关于Serialize这个东东,think in java其实说的很详细,大意如下:

1.Serialize的目的

当你创建对象时,你需要,它一直存在,但是当程序终止时,它就消失了。

如果程序不运行的情况下,可以保存某些信息,这将非常有用。

如何我程序在下次运行的时候,可以把上次运行的某些信息恢复回来.

2.Serialize的使用:

 使用一个嵌套的Serializable对象

package com.joyfulmath.androidstudy.bind.worm;import java.io.Serializable;public class Data implements Serializable {    private int n;  public Data(int n) {    this.n = n;  }  @Override  public String toString() {    return Integer.toString(n);  }    }

package com.joyfulmath.androidstudy.bind.worm;import java.io.Serializable;import java.util.Random;import com.joyfulmath.androidstudy.TraceLog;public class Worm implements Serializable {  static Random rand = new Random(47);  Data[] d = {      new Data(rand.nextInt(10)),      new Data(rand.nextInt(10)),      new Data(rand.nextInt(10))  };    private Worm next;  private char c;    public Worm(int i, char x)  {    TraceLog.i("Worm construct:"+i);    c = x;    if(--i>0)    {      next = new Worm(i,(char) (x+1));    }  }    public Worm()  {    TraceLog.i("default Worm construct");  }  @Override  public String toString() {    StringBuilder result = new StringBuilder(":");    result.append(c);    result.append("(");    for(Data dat:d)    {      result.append(dat+" ");    }    result.append(")");    if(next!=null)    {      result.append(next);    }    return result.toString();  }    }

验证序列化的读写:

import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import com.joyfulmath.androidstudy.TraceLog;public class WormSample {    static final String path = "/mnt/sdcard/worm.out";  public void doAction()  {    Worm w = new Worm(6, 'a');    TraceLog.i("\n"+w.toString());        try {      ObjectOutputStream opt = new ObjectOutputStream(new FileOutputStream(path));      opt.writeObject("Worm object\n");      opt.writeObject(w);      opt.close();      ObjectInputStream in = new ObjectInputStream(new FileInputStream(path));      String s = (String) in.readObject();      Worm w2 = (Worm) in.readObject();      TraceLog.i(s+w);    } catch (FileNotFoundException e) {      // TODO Auto-generated catch block      e.printStackTrace();    } catch (IOException e) {      // TODO Auto-generated catch block      e.printStackTrace();    } catch (ClassNotFoundException e) {      // TODO Auto-generated catch block      e.printStackTrace();    }  }}

最后log:

08-15 09:18:20.384: I/Worm(28437): <init>: Worm construct:6 [at (Worm.java:21)]08-15 09:18:20.384: I/Worm(28437): <init>: Worm construct:5 [at (Worm.java:21)]08-15 09:18:20.384: I/Worm(28437): <init>: Worm construct:4 [at (Worm.java:21)]08-15 09:18:20.384: I/Worm(28437): <init>: Worm construct:3 [at (Worm.java:21)]08-15 09:18:20.384: I/Worm(28437): <init>: Worm construct:2 [at (Worm.java:21)]08-15 09:18:20.384: I/Worm(28437): <init>: Worm construct:1 [at (Worm.java:21)]08-15 09:18:20.384: I/WormSample(28437): doAction: 08-15 09:18:20.384: I/WormSample(28437): :a(853):b(119):c(802):d(788):e(199):f(881) [at (WormSample.java:18)]08-15 09:18:20.414: I/WormSample(28437): doAction: Worm object08-15 09:18:20.414: I/WormSample(28437): :a(853):b(119):c(802):d(788):e(199):f(881) [at (WormSample.java:28)]

可以看到,数据被很好的还原了,包含内部的序列化对象!

 

二:parcel

Serializable是java定义的一套序列化机制,但是他是操作文件来执行的。或者说,它的性能无法满足android上的要求,

这样,parcel被google发明出来,用以取代Serializable。

1.Parcelable 的使用

package com.joyfulmath.androidstudy.bind.worm;import android.os.Parcel;import android.os.Parcelable;public class DataP implements Parcelable {  public int n;    public DataP(int n) {    this.n = n;  }  @Override  public int describeContents() {    return 0;  }  @Override  public void writeToParcel(Parcel dest, int flags) {    dest.writeInt(n);  }    public static final Parcelable.Creator<DataP> CREATOR = new Parcelable.Creator<DataP>()   {    public DataP createFromParcel(Parcel in)     {      return new DataP(in);    }    public DataP[] newArray(int size)     {      return new DataP[size];    }  };    private DataP(Parcel in)   {    n = in.readInt();  }  @Override  public String toString() {    return Integer.toString(n);  }    }

package com.joyfulmath.androidstudy.bind.worm;import java.util.Random;import com.joyfulmath.androidstudy.TraceLog;import android.os.Parcel;import android.os.Parcelable;public class WormP implements Parcelable {  static Random rand = new Random(47);  public DataP[] d = { new DataP(rand.nextInt(10)), new DataP(rand.nextInt(10)),      new DataP(rand.nextInt(10)) };  private WormP next;  public byte c;  public WormP(int i,byte x)  {    TraceLog.i("Wormp construct:"+i);    c = x;    if(--i>0)    {      next = new WormP(i,(byte) (x+1));    }  }    @Override  public int describeContents() {    return 0;  }  @Override  public void writeToParcel(Parcel dest, int flags) {    dest.writeByte(c);    dest.writeParcelableArray(d, 0);    if (next != null) {      dest.writeParcelable(next, 0);    }  }  public static final Parcelable.Creator<WormP> CREATOR = new Parcelable.Creator<WormP>() {    public WormP createFromParcel(Parcel in) {      return new WormP(in);    }    public WormP[] newArray(int size) {      return new WormP[size];    }  };  private WormP(Parcel in) {    c = in.readByte();    d = (DataP[]) in.readParcelableArray(DataP.class.getClassLoader());  }    @Override  public String toString() {    StringBuilder result = new StringBuilder(":");    result.append(c);    result.append("(");    for(DataP dat:d)    {      result.append(dat+" ");    }    result.append(")");    if(next!=null)    {      result.append(next);    }    return result.toString();  }}

parcel一般使用在intent的内容的传递,所以本处做一个简单的模拟:

    public void doActionP()  {    TraceLog.i();    byte a = 'a';    WormP w = new WormP(6, a);    TraceLog.i(w.toString());    Intent intent = new Intent();    intent.putExtra("wormp", w);        ///...        Intent newIntent = new Intent(intent);        WormP w2 = newIntent.getParcelableExtra("wormp");    TraceLog.i(w2.toString());        TraceLog.i("end");  }

08-15 10:14:11.924: I/WormSample(20183): doActionP: [at (WormSample.java:47)]08-15 10:14:11.934: I/WormP(20183): <init>: Wormp construct:6 [at (WormP.java:21)]08-15 10:14:11.934: I/WormP(20183): <init>: Wormp construct:5 [at (WormP.java:21)]08-15 10:14:11.934: I/WormP(20183): <init>: Wormp construct:4 [at (WormP.java:21)]08-15 10:14:11.934: I/WormP(20183): <init>: Wormp construct:3 [at (WormP.java:21)]08-15 10:14:11.934: I/WormP(20183): <init>: Wormp construct:2 [at (WormP.java:21)]08-15 10:14:11.934: I/WormP(20183): <init>: Wormp construct:1 [at (WormP.java:21)]08-15 10:14:11.934: I/WormSample(20183): doActionP: :97(8 5 3 ):98(1 1 9 ):99(8 0 2 ):100(7 8 8 ):101(1 9 9 ):102(8 8 1 ) [at (WormSample.java:50)]08-15 10:14:11.934: I/WormSample(20183): doActionP: :97(8 5 3 ):98(1 1 9 ):99(8 0 2 ):100(7 8 8 ):101(1 9 9 ):102(8 8 1 ) [at (WormSample.java:59)]08-15 10:14:11.934: I/WormSample(20183): doActionP: end [at (WormSample.java:61)]

可以看到结果,数据完全正确。

以上就是parcel的使用方式,在下一篇,将探索parcel的实现方式。

 

参考:

http://blog.csdn.net/niu_gao/article/details/6451699